In vitro evaluation of antiviral and anti-inflammatory activities of selected flavonoids against ISKNV infection in Asian seabass cell line.

Flavonoids are natural bioactive compounds with well-documented antiviral, antioxidant, and anti-inflammatory properties, making them promising candidates for disease management in aquaculture. Infectious spleen and kidney necrosis virus (ISKNV) is a major pathogen affecting Asian seabass (Lates calcarifer), leading to significant economic losses. This study investigated the in vitro antiviral, antioxidant, and anti-inflammatory activities of curcumin, quercetin, and epigallocatechin gallate (EGCG) against ISKNV infection in Asian seabass. The virus was propagated in SISS cells, where it induced characteristic cytopathic effects. Cytotoxicity assays demonstrated a dose-dependent response, with quercetin exhibiting the highest cytotoxic potency. Antiviral activity was evaluated through EC50 determination and quantitative PCR analysis, revealing that all three flavonoids significantly inhibited viral replication. Mechanistically, flavonoid treatment upregulated interferon-stimulated genes (ISGs), which play a pivotal role in the host's innate immune defence against viral infections. Furthermore, the flavonoids exhibited strong antioxidant effects by reducing reactive oxygen species (ROS) accumulation in infected cells, thereby mitigating oxidative stress associated with ISKNV infection. Anti-inflammatory effects were evidenced by the suppression of cyclooxygenase (COX) activity, nitric oxide (NO) production, and nuclear factor-kappa B (NF-κB) activation, suggesting their potential to modulate immune responses and attenuate virus-induced inflammation. Gene expression analysis further confirmed the upregulation of antiviral markers and the downregulation of pro-inflammatory cytokines upon flavonoid treatment. These findings underscore the therapeutic potential of flavonoids as antiviral and anti-inflammatory agents against ISKNV, offering a natural and sustainable approach for viral disease management in aquaculture.